Coronary Pressure

Cardiologists must answer three important questions when evaluating and treating patients with a coronary artery stenosis. As a physiologist: "What is the effect of this stenosis on coronary blood flow and myocardial function?"; as a clinician: " Is this lesion responsible for the patient's symptoms?"; and finally as an interventionalist: "Will revascularization of this artery improve the patient?" Fundamentally, the answer to these questions can be given to a large extent by measuring coronary pressure. That is the rationale of writing this book. 1. 1 Historical overview. Andreas Gruentzig and most interventional cardiologists in the early days of PTCA, had the intuitive feeling that pressure measurements could help to establish the severity of a coronary stenosis and to monitor the progress and result of a coronary intervention. At that time, measuring coronary pressure by the balloon catheter was part of a standard procedure. A residual transstenotic gradient of less than 15 mmHg was generally considered as a good result. Later, however, it turned out that measuring these (resting) gradients with balloon catheters was inaccurate an only had a limited prognostic value. Moreover, because there was no consistent theory to correlate pressure measurements to blood flow, the interest in measuring coronary pressures faded and disappeared almost completely with the introduction of new balloon catheters not intended for pressure measurement.

Research centering on blood flow in the heart continues to hold an important position, especially since a better understanding of the subject may help reduce the incidence of coronary arterial disease and heart attacks. This book summarizes recent advances in the field; it is the product of fruitful cooperation among international scientists who met in Japan in May, 1990 to discuss the regulation of coronary blood flow.

Cardiologists must answer three important questions when evaluating and treating patients with a coronary artery stenosis. As a physiologist: "What is the effect of this stenosis on coronary blood flow and myocardial function?"; as a clinician: " Is this lesion responsible for the patient's symptoms?"; and finally as an interventionalist: "Will revascularization of this artery improve the patient?" Fundamentally, the answer to these questions can be given to a large extent by measuring coronary pressure. That is the rationale of writing this book. 1. 1 Historical overview. Andreas Gruentzig and most interventional cardiologists in the early days of PTCA, had the intuitive feeling that pressure measurements could help to establish the severity of a coronary stenosis and to monitor the progress and result of a coronary intervention. At that time, measuring coronary pressure by the balloon catheter was part of a standard procedure. A residual transstenotic gradient of less than 15 mmHg was generally considered as a good result. Later, however, it turned out that measuring these (resting) gradients with balloon catheters was inaccurate an only had a limited prognostic value. Moreover, because there was no consistent theory to correlate pressure measurements to blood flow, the interest in measuring coronary pressures faded and disappeared almost completely with the introduction of new balloon catheters not intended for pressure measurement.

A little bit more than two years after the first edition, we are pleased to publish the second edition of this book. More than half of the chapters have been remodeled and completed as the result of technical improvements and recently acquired clinical data. During these two years, the number of coronary pressure measurements performed worldwide both during diagnostic and interventional procedures has increased almost exponentially. Most of the initial problems associated with this new approach have been overcome. Many colleagues have explored new research avenues and in many catheterization laboratories the method has matured from a research toy to a clinical tool. Classical indications such as the intermediate stenosis and guidance of PTCA or stent implantation, have been largely extended and coronary pressure measurement has proven to be useful in multi vessel disease, diffuse disease, long and serial stenosis, after myocardial infarction, and in many other diagnostic and interventional situations encountered in the catheterization laboratory. Quite unexpectedly, this approach has also enforced the ties with our surgical colleagues in the selection of patients suitable for minimal invasive surgery or hybride revascularization. Also in mild and intermediate left main disease, there is a role for coronary pressure measurement in the process of decision making. We would like to express our gratitude to all those many colleagues who trusted and applied this new approach for the benefit of their patients. Aalst, Eindhoven, Bernard De Bruyne. Nico H. J. Pijls. March, 2000. Table of Contents (overview) 1 1.

by JULIEN IE HOFFMAN One of the earliest coronary physiologists was Scaramucci who, in 1695, postu lated that during systole the contracting myocardium inhibited coronary blood flow. Since then, the many contributions that have been made to our knowledge of the coronary circulation can be arbitrarily divided into three phases based on advances in technical methods. The early phase of research into the coronary circulation, done with great difficulty with crude methods, may be regarded as ending in the 1940s, and it included major discoveries made by such well known investigators as Georg von Anrep, Ernest Starling, Carl Wiggers, and Louis Katz, who formulated much of our basic understanding of the field. After 1940, the field of coronary physiology entered a new phase when instruments for high fidelity registration of coronary flow and pressure became available. This era was domi nated by Donald Gregg who combined careful attention to the function of these instruments (some of which he helped to develop) with an extraordinary ability to discern mechanisms from apparently minor changes in coronary flow and pressure patterns. His book 'The Coronary Circulation in Health and Disease' set a new standard in the field. After 1960, techniques for measuring regional myocardial blood flow became available, and enabled a large group of eminent investigators to make major advances in understanding the physiology and pathophysiology of myocardial blood flow.

The coronary circulation is unique in that it is responsible for maintaining adequate oxygen and substrate delivery to the organ that generates the pressure needed to drive blood throughout the entire circulatory system. In the simplest terms, coronary blood flow is directly proportional to the arterial pressure gradient across the coronary vasculature and inversely proportional to coronary vascular resistance. However, myocardial perfusion is collectively regulated by a complex variety of mechanisms which include: (1) extravascular compressive forces; (2) diastolic time fraction; (3) coronary perfusion pressure; (4) myocardial metabolism (local metabolic factors); (5) endothelial-derived substances; (6) neuro-humoral influences; and (7) arterial oxygen tension and content. This book considers each of these determinants with particular emphasis on the functional interaction between the physical and biological determinants of myocardial perfusion. Pathophysiologic aspects of coronary atherosclerosis and cardiovascular disease states are also considered. Table of Contents: Abbreviations / Acknowledgments / Introduction / Basic Coronary Anatomy / Myocardial-Coronary Interaction / Arterial Pressure and Autoregulation / Local Metabolic Control / Endothelial-Dependent Control / Neural Activation and Circulating Hormones / Coronary Stenosis, Myocardial Ischemia, and Effects of Disease / Summary / Reference List / Author Biography

Covers all of the equations that candidates need to understand and be able to apply when sitting postgraduate anaesthetic examinations.